1886.] 



President's Address. 



383 



contained in Argelander's " Durchmusterung " of the northern 

 hemisphere, and to subsequently reduce the observations so as to 

 complete Argelander's great work by extending it to the southern 

 hemisphere. Professor Kapteyn, in Holland, has nobly undertaken 

 to devote his spare time for seven years to superintending the reduc- 

 tion. Dr. Gill has laid the proposal before the Government Grant 

 Committee. Having regard to the magnitude of the undertaking, 

 and the probability of a conference of astronomers being shortly 

 held in Paris to discuss the whole question, the Government Grant 

 Committee suggested to the Council of the Royal Society that they 

 should appoint a committee to take the subject into consideration, and 

 the Council have acted on this suggestion. Dr. Gill intends to come 

 to Europe in the spring, so that the committee will be able to consult 

 him personally. 



This morning I received through the Foreign Office an invitation 

 from the Academie des Sciences for myself, or some other Delegate of 

 the Royal Society, to attend the conference to which I have already 

 referred, which is fixed for the 16th of April. I shall take the first 

 opportunity of consulting the new Council as to their wishes. 



The Coplejr Medal for this year has been awarded to the veteran in 

 science, our foreign member, Professor Pranz Ernst Neumann, for 

 his researches in theoretical optics and electro-dynamics. 



Having in his earlier years treated of crystallographic subjects, 

 he more than half-a-century ago turned his attention to the theory 

 of light. Presnel had, with his wonderful sagacity, arrived at his 

 celebrated laws of double refraction from the theory of transverse 

 vibrations, aided by conceptions derived from a dynamical theory 

 which was only in part rigorous. Cauchy and Neumann, indepen- 

 dently of each other, were the first to deduce from a rigorous 

 dynamical calculation, applied to a particular hypothesis as to the 

 constitution of the ether, laws of double refraction, not indeed 

 absolutely identical with those of Presnel, but closely resembling them. 

 In this case the laws were known beforehand. But in a very elaborate 

 later paper, Professor Neumann deduced from theory the laws of 

 crystalline reflection, laws which appear to agree with the observa- 

 tions of Seebeck, and which had not been discovered by Fresnel, 

 though some of them were independently and about simultaneously 

 obtained by MacCullagh. 



Professor Neumann is perhaps still better known in connexion with 

 the theory of electrodynamics, and the mathematical deduction of the 

 laws of induced currents due to the motion of the primary and 

 secondary conductor. He may be said to have completed for the 

 induction of currents the mathematical treatment which Ampere 

 had applied to their mechanical action. 



Of the two Royal Medals, it is the usual, though not invariable, 



